Pump system for conveying lubricating oil

ABSTRACT

A pump system for conveying lubricating oil to a cutting chain of a chain saw is provided. The pump system comprises at least one first oil pump, wherein a quantity of oil being conveyed thereby is adjustable by an operator of the chain saw. The pump system also includes a basic oil pump that is connected in parallel to the adjustable oil pump.

BACKGROUND OF THE INVENTION

The present invention relates to a pump system for conveying lubricatingoil to a cutting chain of a chain saw.

Chain saws have a guide bar on the peripheral edge of which is guided acutting chain having individual chain links. The pivotable connection ofthe chain links, as well as the cutting teeth, are subjected to highstresses during operation. To avoid excessive wear, and to achieve animproved cutting result, a lubricating oil is supplied to the cuttingchain via a pump system.

A certain quantity of oil is desired depending upon the material that isto be cut. With different types of wood that are to be cut, it has beenshown that different quantities of lubricating oil are expedient for agood cutting result. For this purpose, pump systems are known having oilpumps that can be adjusted by an operator, where the operator of a chainsaw can adapt the quantity of lubricating oil being supplied to thematerial that is to be cut.

It has been shown that the capacity of an oil pump is a function of theviscosity of the oil. However, this can change during operation. Forexample, heating of the lubricating oil due to external influences, suchas weather or a brief heating due to the operating temperature of adrive motor, can lead to a considerable reduction of the viscosity. Athereby resulting, and possibly considerable, fluctuation of thecapacity is to be compensated for by the operator by regulating theadjustable oil pump. It is also desired to be able to compensate forfluctuations of the capacity when changing the type of oil.

It has been shown that the viscosity-dependent capacity is subjected tounexpectedly high fluctuations. An at least approximately optimum oilcapacity at operating temperature can, after a longer period ofinterruption of operation, and with the lubricating oil cooled off,result in the initially conveyed quantity of oil being too little. Anexcessive wear of the cutting chain can result. Similarly, if thequantity of oil conveyed is too low, the cutting result can beunsatisfactory.

It is therefore an object of the present invention to improve a pumpsystem in such a way that a reliable lubrication of the cutting chain isensured over a large operating range.

BRIEF DESCRIPTION OF THE DRAWINGS

This object, and other objects and advantages of the presentapplication, will appear more clearly from the following specificationin conjunction with the accompanying schematic drawings, in which:

FIG. 1 is a longitudinal cross-sectional illustration of one exemplaryembodiment of an inventive pump system having two integrated pumps andtwo monolithically formed pistons in the lower dead center position;

FIG. 2 shows the arrangement of FIG. 1 with the piston arrangement inthe upper dead center position;

FIG. 3 shows the arrangement of FIGS. 1 and 2 with the line valveclosed;

FIG. 4 shows, in a cross-sectional illustration, details of therotatable piston of the arrangement of FIGS. 1 to 3;

FIG. 5 shows the arrangement of FIG. 4 with the piston rotated by 180°;

FIG. 6 is a longitudinal cross-sectional illustration of a variation ofan adjustable oil pump with a piston in the upper dead center position,set to a low piston displacement;

FIG. 7 shows the arrangement of FIG. 6 with the piston in the lower deadcenter position;

FIG. 8 shows the arrangement of FIG. 6 at maximum piston displacement;and

FIG. 9 shows the arrangement of FIG. 7 at maximum piston displacementand with the piston in the lower dead center position.

SUMMARY OF THE INVENTION

The pump system of the present application comprises at least one firstoil pump, wherein a quantity of oil being conveyed thereby is adjustableby an operator of the chain saw, and a basic oil pump, which isconnected in parallel to the adjustable oil pump.

Thus, a pump system is proposed according to which a basic oil pump isconnected in parallel to at least one adjustable oil pump. In thisconnection, the basic oil pump conveys a basic quantity of oil that evenunder cold operating conditions, and a lubricating oil that has acorrespondingly high viscosity, ensures a basic supply of lubricatingoil to the cutting chain. By means of the oil pump that is connected inparallel and that can be adjusted by an operator, an additional quantityof oil can be supplied to the cutting chain as a function of need. Inthis connection, there is no adverse impact upon the basic supply viathe basic oil pump. An incorrect setting of the adjustable oil pump, oreven changing environmental conditions, do not lead to an undersupply oflubricating oil.

It can be expedient to make the basic oil pump adjustable. For example,by adjusting the basic oil pump it can be possible to adapt the basiccapacity to a specific type of wood or to a specific type of lubricatingoil, whereas via the adjustable oil pump fluctuations of the operatingparameters, for example as a consequence of fluctuations in viscositydue to the temperature, are compensated for. Pursuant to an expedientfurther development, the capacity of the basic oil pump is fixed. Thisprevents the user from unintentionally making an incorrect adjustment.The adjustable oil pump advantageously has a reduced maximum capacity incomparison to the basic oil pump. Incorrect adjustments of the pumpsystem are prevented via the appropriately small adjustment range.

Pursuant to an advantageous further development, the oil pump isembodied as a piston pump having a piston portion that can be rotatablydriven about its longitudinal axis, whereby a peripheral inclined grooveis provided on the piston portion into which a control pin that is fixedto a housing in the axial direction extends. The piston portion can becontinuously rotatably driven, whereby via the control pin and theinclined groove, an oscillating axial movement is produced with littlemechanical effort. Such a pump has a straightforward construction andfurthermore has a good service life with little mechanical wear.

Pursuant to an expedient further development, a respective piston of thetwo pumps is fixed in position on a common piston portion, and in sodoing is in particular monolithically embodied with the piston portion.To drive the two pistons, only one corresponding piston portion isrequired. The pump is embodied as an integral component that is compactand straightforward. Only a single drive is necessary for both pumps. Inthis connection, the pistons advantageously have different diameters,whereby they are guided in a correspondingly stepped cylinder bore thatis provided in a pump housing that in particular has a monolithicconfiguration. The different pump diameters lead to different capacitiesfor the two pumps, whereby the smaller piston diameter, in conjunctionwith the adjustable oil pump, leads in a desired manner to a reducedmaximum conveying capacity. With a stepped cylinder bore, the sealinglyguided piston having the smaller diameter at the same time also effectsa sealing of the cylinder space in which the larger piston is guided.Separate sealing means are not necessary. The pump has a straightforwardconstruction and is economical to manufacture.

For an easy adjustability of the oil conveying capacity, the arrangementof a line valve, especially on the intake side of the adjustable oilpump, can be expedient. A line valve has a straightforward construction,and due to the arrangement on the intake side prevents pressure peaks inthe pump when the valve is closed. The line valve can be embodied as acontrol valve, by means of which an additional quantity of oil canselectively be activated or deactivated. Pursuant to an expedientfurther development, the line valve is embodied as a control valve thatis in particular infinitely variable. For this purpose, an embodiment asa rotary piston valve is particularly suitable. The additional quantityof oil that is conveyed via the adjustable oil pump can be regulated ina finely sensitive manner. The mechanical outlay, and hence the cost, islow.

Further specific features of the present application will be describedin detail subsequently.

DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring now to the drawings in detail, FIG. 1, in a cross-sectionalillustration, shows a pump system for conveying lubricant or lubricatingoil 1 to a cutting chain of a non-illustrated chain saw. The pump systemincludes an oil pump 2, which can be adjusted by a user, as well as abasic oil pump 3. The two oil pumps 2, 3 each have a supply or feedconduit 24, 26, as well as a discharge conduit 25, 27. The lubricatingoil 1 is drawn in via the feed conduits 24, 26, and is discharged viathe discharge conduits 25, 27. The adjustable oil pump 2, and the basicoil pump 3, are connected via their pertaining feed conduits 24, 26 withthe same, non-illustrated oil tank. The two discharge conduits 25, 27lead to the cutting chain of the chain saw, which results in a parallelconnection of the two oil pumps 2,3. Further adjustable oil pumps 2, forachieving a plurality of operating stages, can also be connected inparallel.

The pump system can be configured as a system having geared pumps,diaphragm pumps, or the like, and in the illustrated embodiment isembodied as a system of piston pumps. For this purpose, a piston portion4 having a circular cross-sectional configuration is provided that isrotatable, about an axis of rotation 20, in the direction of the arrow30. The piston portion 4 is sealingly guided in a pump housing 11,whereby in the pump housing a control pin 6 is fixed to the housingrelative to the direction of the axis of rotation 20. The piston portion4 has a peripheral inclined groove 5 into which the control pin 6extends. The inclined groove 5 extends at an angle to a line that isperpendicular to the axis of rotation 20. Due to the rotation of thepiston portion 4 in the direction of the arrow 30, an oscillatingdisplacement or stroke of the piston portion 4 in the direction of itsaxis of rotation 20 is effected via the stationarily held control pin 6that travels in the inclined groove 5. The piston portion 4 is shownapproximately in its lower dead center position, from which, uponfurther rotation, the piston portion 4 carries out an axial movement inthe direction of the arrow 19.

Monolithically formed on the piston portion 4 are two pistons 7, 8having corresponding diameters D₂, D₁, whereby the diameter D₁ of theupper piston 8 is less than the diameter D₂ of the lower piston 7. Thelower piston 7 has the same diameter D₂ as does the remaining pistonportion 4. The two pistons 7, 8 merge with one another in a steppedmanner. In the region of the pistons 7, 8, the piston housing 11 isembodied as a corresponding cylinder 9, 10 via a stepped bore, wherebythe two pistons 7, 8 are slidingly guided in the respective cylinders 9,10 in a sealing manner in both the axial as well as the peripheraldirections.

Provided above the smaller piston 8 is a pump chamber 21 that is filledwith lubricating oil 1 during operation, and that is delimited by thepiston 8 and the pump housing 11. Opening into the pump chamber 21 onthe peripheral side of the piston 8 are the pertaining feed conduit 24and discharge conduit 25. The piston 8 is provided on the side with arecess 22 via which, in the illustrated rotational position of thepiston portion 4, the pump chamber 21 communicates in a flow-guidingmanner with the upper discharge conduit 25. Upon displacement of thepiston portion 4 in the direction of the arrow 19, the lubricating oil 1that is disposed in the upper pump chamber 21 is pressed out through thedischarge conduit 25 and is conveyed in the direction of thenon-illustrated saw chain.

The basic oil pump 3 is constructed in a manner comparable to theadjustable oil pump 2. A lower pump chamber 31 of the basic oil pump 3is delimited by the piston 7, the pump housing 11, and on the inner sideby a circumferential wall of the smaller piston 8. By means of a lateralrecess 22 on the piston 7, the lower pump chamber 31 communicates in aflow-guiding manner with the corresponding lower discharge conduit 27.During the displacement of the piston portion 4 in the direction of thearrow 19, lubricating oil 1 that was previously drawn in via the lowerfeed conduit 26 is conveyed out of the lower pump chamber 31 and throughthe lower discharge conduit 25 in the direction of the arrow 29 to thenon-illustrated saw chain.

The diameters of the two pistons 7, 8, or the pertaining cylinders 9,10, are such that with a specified stroke of the piston portion 4, theadjustable oil pump 2 has a smaller maximum capacity than does the basicoil pump 3. The stroke of the piston portion 4, and hence of the twopistons 7, 8, results from the inclined position of the groove 5 inconnection with the fixed mounting of the control pin 6. The feedconduit 26 and the discharge conduit 27 of the basic oil pump 3 areprovided as infrequently as is the automatic control of the pistonportion 4 with an adjustment device. A capacity or delivery of the basicoil pump is thus fixed. The capacity adjustment of the basic oil pump,for an adjustment with regard to the work or by the operator, can alsobe provided, for example via an adjustable stroke of the piston portion4 or by throttle devices provided in the feed conduit 26 or in thedischarge conduit 27.

In the upper region of the pump system, i.e. in the region of the feedand discharge conduits 24-27, the pump housing 11 is surrounded by aline or conduit housing 43. A line valve 12 is disposed in the conduithousing 43 in the region of the upper feed conduit 24. For this purpose,an approximately cylindrical valve body 23 is rotatably mounted in theconduit housing 43. In the illustrated rotational position of the valvebody 23, a bore 14 that extends through the valve body 23 is alignedwith the upper feed conduit 24, which is thus continuously flow-guiding.The valve body 23 has a circumferential groove 15 into which extends alocking pin 16 that is fixed in the conduit housing 43. A valve body 23is thereby secured in the axial direction. An end face of the valve body23 is provided with a slot 18 for receiving a screwdriver or the like. Avalve body 23 can thereby be rotated if necessary, as a result of whichthe bore 14 can be rotated out of its aligned position relative to thefeed conduit 24. As a result, on the intake side of the adjustable oilpump 2, the flow of a feed stream of lubricating oil 1 can becontrolled. To limit the rotational movement of the valve body 23, thelatter is provided with a stop 17. Thus, the flow quantity of the oilpump 2 can be adjusted by an operator.

FIG. 2 shows the arrangement of FIG. 1 with the piston portion 4 rotatedby about 180°. Due to the engagement of the control pin 6 in theinclined groove 5, there results a relative position of the pistonportion 4 relative to the pump housing 11 where the piston portion 4 isdisposed approximately in the upper dead center position. The volumes ofthe pump chambers 21, 31 are minimal. In the illustrated rotationalposition, the recesses 22 face the feed conduits 24, 26, as a result ofwhich these feed conduits communicate with the pump chambers 21, 31 in aflow-guiding manner. The discharge conduits 25, 27 are closed off by theperipheral walls of the pistons 7, 8.

With a further rotation of the piston portion 4 in the direction of thearrow 30 there is effected a downward displacement in the direction ofthe arrow 32. The volumes of the pump chambers 21, 31 consequentlyincrease, as a result of which lubricating oil 1 is drawn in via thefeed conduits 24, 26.

A continuous rotational drive of the piston portion 4 in the directionof the arrow 30 results in an oscillating displacement of the pistonportion 4 in the direction of the arrow 19 (FIG. 1) or the arrow 32(FIG. 2). In conjunction with the alternating flow-guiding communicationof the pump chambers 21, 31 via the recesses 22 either with the feedconduits 24, 26 or with the discharge conduits 25, 27, there is effecteda cyclical operation of the two oil pumps 2,3.

FIG. 3 shows the arrangement of FIG. 1 with the line valve 12 closed.The valve body 23 is rotated by 90° relative to the position shown inFIG. 1. The bore 14 is transverse to the upper feed conduit 24, as aresult of which the latter is closed. The feed of lubricating oil 1through the upper feed conduit 24 into the upper pump chamber 21 isinterrupted. The adjustable oil pump 2 conveys no lubricating oil 1,while the basic oil pump 3 conveys lubricating oil 1 through the lowerdischarge conduit 27 in the direction of the arrow 29 to the cuttingchain.

The valve body 23 is rotatable in an infinitely variable manner, as aresult of which an infinitely variable throttling effect can beestablished by means of a freely selectable relative rotation of thebore 14 relative to the feed conduit 24. The line valve 12 is thereby aninfinitely variable control valve. Due to the illustrated rotatablevalve body 23, the control valve 13 is embodied as a rotary pistonvalve. It can also be expedient to provide a linearly displaceable valvebody 23, a butterfly valve, an adjustable orifice plate, or the like. Acontrol valve that can be switched into two or more prescribed positionscan also be expedient.

In the illustrated embodiment, the pump system is embodied as anintegrated system of the two oil pumps 2, 3 with a common pump housing11, conduit housing 43, and monolithic piston portion 4. Two separateoil pumps 2, 3 having a different or the same construction can also beprovided. For example, with a separated configuration of the two oilpumps 2, 3, the basic pump 3 can have a fixed stroke or displacement,and the adjustable oil pump can have a variable displacement, of thecorresponding piston 7, 8. A configuration corresponding to that ofFIGS. 6 to 9 can, for example, be suitable for this purpose.

The schematic cross-sectional illustration of FIG. 4 shows thearrangement of FIG. 2 in the region of the upper piston 8. In theillustrated rotational position of the piston 8, which is rotatablydriveable in the direction of the arrow 30, the feed conduit 24communicates in a flow-guiding manner with the lateral recess 22 of thepiston 8. At the same time, the discharge conduit 25 is closed off bythe peripheral wall of the piston 8. With a downward movement of thepiston 8, lubricating oil 1 (FIG. 2) flows in the direction of the arrow33 to the recess 22, and from there into the upper pump chamber 21 (FIG.2).

FIG. 5 shows the arrangement of FIG. 4 with the piston 8 rotated by180°. The feed conduit 24 is closed off by the peripheral wall of thepiston 8. The discharge conduit 25 communicates in a flow-guiding mannerwith the recess 22. With an upward movement of the piston 8, lubricatingoil 1 flows out of the upper pump chamber 21 (FIG. 1) via the recess 22and through the discharge conduit 25 in the direction of the arrow 28.

The schematic illustration of FIG. 6 shows a further embodiment of anoil pump, the capacity of which can be adjusted. The illustrated oilpump can be utilized by itself or in a pump system pursuant to FIGS. 1to 5. The details for the control of the oil flow via the rotatablepiston portion 4, although not shown in detail here, can be embodiedsimilar to that of FIGS. 1 to 5.

Mounted on a free end of the piston portion 4 is a gear wheel or pinion36 having an inclined toothing. The gear wheel 36 is provided forengagement in a drive worm, as a result of which the piston portion 4can be rotatably driven about its axis of rotation 20 in the directionof the arrow 30. The piston portion 4 is rotatably and longitudinallydisplaceably mounted in the pump housing 11. The control pin 6 extendsinto the inclined groove 5, whereby from the rotational movement in thedirection of the arrow, an oscillating displacement of the pistonportion 4 is effected in the direction of the double arrow 44.

In the illustrated embodiment, the control pin 6 is displaceablyembodied in the direction of the double arrow 35 in a radial directionrelative to the axis of rotation 20. For this purpose, the control pin 6is provided with a shaft 38, which is longitudinally displaceablymounted in the housing 11. The longitudinally displaceable mounting canbe effected, for example, via a non-illustrated thread. With a rotationof the control pin 6, for example at a head 39, a radial displacement ofthe control pin 6 in the direction of the double arrow 35 can beeffected.

Disposed at that end of the shaft 38 that faces the piston portion 4 isa spherical portion 37 that extends into the inclined groove 5. In theaxial direction, and on the sides, the inclined groove 5 is delimited byessentially planar groove walls 41, 42 that extend parallel to oneanother and are inclined relative to a line that is perpendicular to theaxis of rotation 20. The spherical portion 37 extends in an essentiallyplay-free manner, or with little play, between the groove walls 41, 42,which results in an automatic control of the piston portion 4 in adirection of the double arrow 44.

A rotational movement of the piston portion 4 in the direction of thearrow 30 results, in an oscillating manner, in a change of the inclinedposition of the groove walls 41, 42 relative to the spherical portion37. Due to the spherical surface, a rolling movement of the groove walls41, 42 along the spherical portion 37 is effected in a wear-reducingmanner.

The control pin 6 is shown in a radial position in which the sphericalportion 37 is disposed close to the axis of rotation 20. From FIG. 7 itcan be seen that with a rotation of 180°, in conjunction with theinclined position of the groove walls 41, 42, the piston portion 4carries out a displacement h₁.

FIG. 8 shows the arrangement of FIG. 6 with thecontrol pin 6 displacedradially outwardly. In this connection, the spherical portion 37 isdisposed approximately in a ball-receiving means 40 of the pump housing11, whereby, however, it still extends into the inclined groove 5. Fromthe increased radial spacing of the spherical portion 37 relative to theaxis or rotation 20, there is effected in conjunction with the inclinedposition of the groove walls 41, 42, in the illustrated upper deadcenter position of the upper pump chamber 21, a reduced volume relativeto the volume of FIG. 6. In the illustrated embodiment, the end face ofthe piston 8 rests approximately against the pump housing 11.

FIG. 9 shows the arrangement of FIG. 8 with the piston portion 4 rotatedby about 180°. In this connection, the piston portion 4 is disposed inthe lower dead center position, whereby from the increased radialspacing of the spherical portion 37 relative to the axis of rotation 20there results an increased displacement h₂ in comparison to the positionof FIGS. 6 and 7. In the illustrated lower dead center position, thevolume of the upper pump chamber 21 is thus greater than in the lowerdead center position of FIG. 7 where the control pin is displacedinwardly. The stroke or displacement space resulting from thedisplacement h₁ or h₂ thus increases approximately linearly relative tothe radial spacing of the spherical portion 37 from the axis of rotation20. The conveying capacity of the illustrated oil pump is thereforeapproximately a linear function of the displacement space, and hence isadjustable via the radial position of the control pin 6 relative to theaxis of rotation 20.

The control pin 6 can also be displaced radially outwardly to such anextent that the spherical portion 37 is disposed entirely in theball-receiving means and thus no longer extends into the inclined groove5. This makes it easy to assemble or disassemble the piston portion 4.

With regard to the remaining features and reference numerals, thearrangement of FIGS. 6 to 9 corresponds to the arrangement of FIGS. 1 to5.

The specification incorporates by reference the disclosure of Germanpriority document 103 35 280.5 filed 01 Aug. 2003.

The present invention is, of course, in no way restricted to thespecific disclosure of the specification and drawings, but alsoencompasses any modifications within the scope of the appended claims.

1. A pump system for conveying lubricating oil to a cutting chain of achain saw, comprising: at least one first oil pump, wherein a quantityof oil being conveyed thereby is adjustable by an operator of said chainsaw; and a basic oil pump that is connected in parallel to saidadjustable first oil pump.
 2. A pump system according to claim 1,wherein a capacity of said basic oil pump is fixed.
 3. A pump systemaccording to claim 2, wherein said at least one adjustable first oilpump has a lower maximum capacity than does said basic oil pump.
 4. Apump system according to claim 1, wherein said oil pumps are pistonpumps having a piston portion that is rotatably driveable about alongitudinal axis thereof, wherein a circumferential inclined groove isprovided on said piston portion, and wherein a control pin that isfixedly held in an axial direction in a housing of said pump systemextends into said inclined groove.
 5. A pump system according to claim4, wherein a respective piston of said oil pumps is fixed in position ona common piston portion.
 6. A pump system according to claim 5, whereinsaid pistons are monolithically formed with said piston portion.
 7. Apump system according to claim 5, wherein a pump housing is provided,wherein said pistons have different diameters, and wherein said pistonsare guided in a stepped cylinder bore in said pump housing.
 8. A pumpsystem according to claim 7, wherein said pump housing has a monolithicconstruction.
 9. A pump system according to claim 1, wherein a linevalve is provided for adjusting a capacity of said at least one firstadjustable oil pump.
 10. A pump system according to claim 9, whereinsaid line valve is disposed on an intake side of said adjustable oilpump.
 11. A pump system according to claim 9, wherein said line valve isa control valve.
 12. A pump system according to claim 11, wherein saidcontrol valve is infinitely variable.
 13. A pump system according toclaim 11, wherein said control valve is a rotary piston valve.